According to different inks used, ordinary marker pens can roughly be categorized as water-based marker pens and oil-based marker pens. In order to prevent a writing tip from becoming dried out and thus unusable from long-term exposure to air, an outer cap is usually used to seal the writing tip of the marker pen. However, two hands are required to uncap and cap a marker pen with the outer cap, which is very inconvenient. Furthermore, when capping or uncapping the writing tip, the outer cap can be easily lost along with any hope of preventing the writing tip from drying out. In order to resolve these issues related to using the outer cap, a capless retractable marker pen has been developed. Typically, the cover of the capless retractable marker pen is hidden within the pen tube, and the protracting and retracting of the writing tip is controlled by an actuating means installed in the top of the pen tube. Therefore, compared with the marker pen with an outer cap, the capless retractable marker pen has a superior competitive advantage on the market.
FIG. 1 illustrates a partial cross section showing a conventional capless retractable marker pen. The conventional capless retractable marker pen 100 comprises a pen tube 110, a sheath 120, a writing member 130 and an opening and closing device 140. The pen tube 110 has an upper opening (not shown) and a lower opening 113, in which an arc protrusion 115 is set within the pen tube 110, and is parallel to the lower opening 113 and set apart from the lower opening 113 by a distance L. The sheath 120 is installed within the pen tube 110 and has an upper portion 121 and a lower portion 123, in which a diameter D of the upper portion 121 is greater than a diameter d of the lower portion 123. The top of the upper portion 121 is a closed end (not shown), and the bottom of the lower portion 123 is an open end 127. Typically, the writing member 130 is coaxially disposed within the sheath 120 and has an upper portion 131 and a lower portion 133. The upper portion 131 of the writing member 130 is disposed within the upper portion 121 of the sheath 120 for absorbing and storing ink. The lower portion 133 of the writing member 130 is disposed within the lower portion 123 of the sheath 120, in which a portion of the lower portion 133 extends into the upper portion 121. The lower portion 133 of the writing member 130 extends out of the open end 127 in the lower portion 123 of the sheath 120 to expose a writing tip 135. The ink is transported from the upper portion 131 to the writing tip 135 through the lower portion 133 by capillarity.
In the conventional capless retractable marker pen designs, various opening and closing devices are used to replace the outer cap for achieving the purpose of protracting and retracting a writing tip. For example, the opening and closing device 140 comprises a supporting device 141, a sealing member 161, a plastic filament 169 and a spring member 170. Referring to FIG. 2, which is a three-dimensional diagram of a conventional opening and closing device, the supporting device 141 is installed outside the lower portion 123 of the sheath 120. The supporting device 141 has an upper opening 143 and a lower opening 145, and a sidewall 147 of the supporting device 141 is set with two opposite grooves 149 extending from the upper opening 143. The sealing member 161 covers the writing tip (not shown) and includes a cover plate 163 and a cover supporting tube 165, and a side 164 of the cover plate 163 is movably deposed on a side 166 of the cover supporting tube 165. A sidewall of the cover supporting tube 165 is set with two opposite channels 167. The plastic filament 169 passes and is deposed in the grooves 149 of the supporting device 141, the cover plate 163 and the channels 167, and is clipped into the channels 167. A spring 170 is coaxially deposed outside the lower portion 123 of the sheath 120 and within the supporting device 141. The spring 170 shores the supporting device 141 and the cover supporting tube 165 by elastic force and tightly buckles the supporting device 141 and the sealing member 161 by the plastic filament 169, so as to make the cover plate 163 cover a lower surface 168 of the cover supporting tube 165 to seal the writing tip (not shown).
FIG. 3(A) illustrates an opening action of a cover plate of an opening and closing device of a conventional capless retractable marker pen. When the sheath 120 and the writing tip 135 are moved downward by using an actuating means (not shown) installed on the top of the sheath 120, the opening and closing device 140 descends to the arc protrusion 115 in the pen tube 110 along the direction shown by an arrow 171, and the sealing member 161 continuously rises along the direction shown by the arrow 171 to make the plastic filament 169 loosened gradually. The cover plate 163 is opened resulting from the loosening of the plastic filament 169, so as to make the writing tip 135 project from the cover supporting tube 165 for writing.
FIG. 3(B) illustrates a closing action of a cover plate of an opening and closing device of a conventional capless retractable marker pen. After writing, the sheath 120 and the writing tip 135 are moved upwardly by using the actuating means (not shown), the supporting device 141 continuously rises along the direction shown by an arrow 173, and the sealing member 161 descends relatively to make the plastic filament 169 tighten gradually, so that the lower surface 168 of the cover supporting tube 165 is covered by the cover plate 163 to seal the writing tip 135. In brief, the opening and closing device for the conventional capless retractable marker pen is based on a two-stage design, which combines the supporting device 141, the sealing member 161, the plastic filament 169 and the spring 170, for achieving the purpose of protracting and retracting the writing tip.
The examples that use any of the various opening and closing devices, such as the disclosure in Taiwan patent No. 341,920, the disclosure in U.S. Pat. No. 4,969,764 and the disclosure in U.S. Pat. No. 4,560,298, are hereby incorporated by reference herein in their entirety.
However, the conventional capless retractable marker pens still have many problems requiring solving. The assembling of the opening and closing device of the conventional capless retractable marker pens is done by hand to put the plastic filament 169 on the grooves 149 of the supporting device 141, the cover plate 163 and the channels 167, so that the assembling process is complicated, time-consuming, and the difficult to be sped up in mass production. Furthermore, the opening and closing effect of the opening and closing device is degraded by the elastic fatigue of the plastic filament 169 after being used for a period of time.
It would therefore be desirable for the designers, the users and the manufacturers of pens to improve the structure of the conventional opening and closing device to simplify the manufacture and assembly and thereby increase the manufacturing speed and the yield.